Exemplary embodiments of the invention generally relate to rotary wing aircrafts, and more particularly, to a control system for pitching the blades of a rotor on a rotary wing aircraft.
Control of a rotary wing aircraft is affected by varying the pitch of the rotor blades individually as the rotor rotates and by varying the pitch of all of the blades together. These are known respectively as cyclic and collective pitch control. Blade pitch control of a rotary wing aircraft main rotor is commonly achieved through a swashplate.
The swashplate is typically concentrically mounted about the rotor shaft. The swashplate generally includes two rings connected by a series of bearings with one ring connected to the airframe (stationary swashplate). The rotating ring is connected to the rotor hub through a pivoted link device typically referred to as “scissors”, with the static ring similarly connected to the airframe. The rotating swashplate rotates relative the stationary swashplate. Apart from rotary motion, the stationary and rotating swashplate otherwise move as a unitary component. Cyclic control is achieved by tilting the swashplate relative to a rotor shaft and collective control is achieved by translating the swashplate along the rotor shaft.
Pitch control rods mounted between the main rotor blades and the rotating swashplate transfer loads between the swashplate and the main rotor blades. Main rotor servos extend between and attach to the stationary swashplate and the aircraft fuselage. Displacement of the main rotor servos results in displacement of the stationary swashplate. Hence, by actuating selected main rotor servos, collective and cyclic commands are transferred to the rotor head as vertical and/or tilting displacement of the swashplates.
While swashplate systems are well-known in the art, they are large, heavy, complex, and prone to failure. The bearings necessary to transfer motion from the swashplate to the blades need lubrication and therefore may fail. In addition, mechanical and hydraulic systems have higher failure rates and require more maintenance that electrical systems.